1. Field of the Invention
The present invention relates to a tape feeder for a part mounter, and more particularly, to a tape feeder for a part mounter which can supply electronic parts at compact density and is improved in its indexing function.
2. Description of the Related Art
A typical part mounter is automated equipment used to mount electronic parts such as a semiconductor chip on a printed circuit board. This part mounter supplies component parts in various ways and mounts the parts on a printed circuit board using a suction nozzle which is operated by a robot. The manner of supplying parts varies according to operating conditions and the characteristics of the parts. For example, large parts are supplied by being carried on a tray but small parts do not require a tray. In particular, very small parts are frequently lost or damaged during mounting, and thus require a special tape feeder.
A tape feeder uses a tape reel where parts are attached at predetermined intervals on a tape. In order for the tape feeder to supply parts, a tape must be released from the reel, and a cover must be removed from parts attached to the tape A suction nozzle of a robot absorbs the parts attached to the tape from which the cover has been removed, thereby separating the parts from the tape and moving the separated parts to certain positions on the printed circuit board.
FIG. 1 is an exploded perspective view of a typical tape feeder for a part mounter.
Referring to FIG. 1, the tape feeder includes a guide frame 11, a front cover 12 installed on the front surface of the guide frame 11, and a back cover 13 which covers the rear surface of the guide frame 11. The front and rear surfaces of the guide frame 11 have various parts for helping the tape feeder function. A portion of the guide frame 11 is cut away, and a driving motor 16 is installed in the open portion. A worm gear 17 is installed around the rotation shaft of the driving motor 16. A peel roller 18 and a pinch roller 19 are installed in such a manner that they come into contact with each other. An axle gear 23 is installed on the rear surface of the guide frame 11 coaxially with respect to the peel roller 18. A gear train comprised of a plurality of gears 17, 27, 28129 and 23 (see FIG. 2) is installed on the rear surface of the guide frame 11 and thus transfer the rotation driving force of the motor 16 to the axle gear 23.
A take-up reel 24 is formed on the front surface of the guide frame 11. The take-up reel 24 is also rotated by receiving the driving force of the driving motor 16. A cover on a tape to which parts are attached is wound around the take-up reel 24. That is, after the cover is separated from the tape, it is wound around the takeup reel 24.
A shield 14 covering the rear surface of the guide frame 11, and a printed circuit board 15 having various electronic parts formed thereon are interposed between the guide frame 11 and the back cover 13.
A sensor (not shown) is installed on the upper portion 22 of a stripper 20 on the guide frame 11. The sensor senses arrival of a part at a suction position, and accordingly, the suction nozzle separates parts from the tape and transfers them to certain positions. The stripper 20 is installed on the upper portion of the guide frame 11 by being elastically supported by a stabilizer spring 21. One end of a compression spring 21' is supported by the lateral surface of the stripper 20, and the other end thereof is inserted into a boss (not shown) formed on the guide frame 11.
Some parts of upper portion of the front cover 12 is cut out to avoid collision with the stripper 20 when the front cover 12 is installed on the guide frame 11. A magnified view of the front cover 12 is shown in FIG. 5. That is, the stripper 20 is separately manufactured, and part of the upper portion of the front cover 12 is cut out as shown in FIG. 1 to install the stripper 20 on the upper lateral portion of the guide frame 11.
FIG. 2 is an exploded perspective view of the rear surface of the guide frame 11.
Referring to FIG. 2, a pulley 25 is installed on the rear surface of the guide frame 11, and first, second and third gears 27, 28 and 29 are installed in mesh with each other thereon. The third gear 29 is engaged with the axle gear 23. The worm gear 17 of the motor 16 shown in FIG. 1 is engaged with the first gear 27. A pulley (not shown) around which a belt 26 is to be wound is installed on the first gear 27. The belt 26 is also wounded around the pulley 25. The pulley 25 is installed coaxially with respect to the take-up reel 24 (see FIG. 1) installed on the front surface of the guide frame 11. The axle gear 23 is installed coaxially with respect to the peel roller 18 (see FIG. 1). Accordingly, the rotating force of the motor 16 rotates the take-up reel 24 through the first gear 27, the belt 26 and the pulley 25, and rotates the axle gear 23 through the first through third gears 27 through 29 to thereby rotate the peel roller 18. Reference numeral 31 is a lever. The lever 31 is installed to be capable of being pivoted while receiving an elastic force from a spring 33, A lower end 31a of the lever 31 is fit into a groove on the mounting portion of an unshown chip mounter, thus constantly positioning the entire part feeder on the chip mounter.
FIG. 3 is a schematic exploded perspective view of the first through third gears and a sprocket 32.
Referring to FIG. 3, the sprocket 32 is coaxially installed on the third gear 29. The sprocket 32 is shaped with a plurality of saw teeth 41 and a plurality of slots 42 around the circumference as shown in FIG. 4. The saw teeth 41 can be seen on the front side of the guide frame 11 through a cut-off portion of the guide frame 11, and the saw teeth 41 of the sprocket 32 seen through the guide frame 11 lies under the stripper 20 shown in FIG. 1. The saw teeth 41 of the sprocket 32 are inserted into grooves formed on a tape, and accordingly, when the sprocket 32 rotates, the tape is released from the reel and moves forward at predetermined pitches. To be more specific, a plurality of holes are formed along the edge of the tape onto which parts are attached, and the saw teeth 41 of the sprocket 32 are inserted into these holes, and the tape moves forward along a predetermined path by the rotation of the sprocket 32. Also, a light emitting sensor (not shown) to be described later is installed, and light emitted from the light emitting sensor passes through the slots 42 of the sprocket 32. That is, a light receiving sensor (not shown) senses whether the light from the light emitting sensor passes through the slots 42 or is blocked by portions other than the slots, whereby the rotation pitch of the sprocket 32 can be determined.
FIG. 6 shows the above-described gears and sensors.
Referring to FlG. 6, an encoder 61 is installed in front of the rotation shaft of the worm gear 17, and a first sensor 62a for sensing rotation of the encoder 61 is installed. A second sensor 62b for sensing rotation of the sprocket 32 described referring to FIG. 4 is installed. The first and second sensors 62a and 62b sense the rotations of the worm gear 17 and the sprocket 32 and transmit corresponding signals to a controller 63, and the controller 63 controls the driving of the motor in response to the signals. Reference numeral 64 represents a part of the traveling path of a tape onto which parts are attached, and reference numeral 65 represents a cover separated from the tape. The cover 65 is wound around the take-up reel 24. In the circle indicated by reference character A, the encoder 61 viewed from the right side of FIG. 6 is shown.
Referring to FIGS. 1 and 6, a tape having parts attached thereto reaches a portion where the stripper 20 is installed, along a predetermined path of a tape feeder. The tape is pressed between the compression spring 21' and a slanted surface contacting the compression spring 21'. A slot is formed through the stripper 20, and a cover covering parts is removed from a parts supply tape through the slot. The cover is inserted between the peel roller 18 and the pinch roller 19 and thus removed from the tape by tension provided from these rollers, and again moves to the take-up reel 24 along a predetermined path and is wound thereby. The sensor (not shown) installed on the portion 22 senses arrival of the parts on the tape at predetermined positions, and accordingly, a part suction nozzle absorbs the parts from the tape and transfers them. The tape 64 with parts removed is again moved along a predetermined path and released to the outside of the tape feeder.
Here, the tape 64 moves along a predetermined path according to a predetermined indexing function, and this movement of the tape 64 is made by the operations of the encoder 61, sprocket 32, and sensors 62a and 62b shown in FIG. 6. That is, when an indexing pitch is determined by detection of an optical signal transmitted through the slots 42 of the sprocket 32 by the second sensor 62b, the first sensor 62a calculates an optical signal detected by the encoder 61 to stop the driving motor 16. In this way, the indexing function is accomplished.
This general tape feeder has the following problems.
First, many parts cannot be attached to the tape because of the relatively large minimum rotation pitch of the sprocket 32. The indexing pitch of the sprocket 32 depends on the slots 42 formed through the sprocket 32, and the very wide interval between adjacent slots 42 increases the rotation pitch of the sprocket 32. Accordingly, the number of parts that can be attached is reduced. Also, since parts can be mounted only on one surface of the printed circuit board 15 shown in FIG. 2, the tape feeder overall becomes thicker. That is, since parts are mounted only on the opposite surface of a surface of the printed circuit board 15 facing the shield 14, the parts are installed on a restricted space, thereby increasing the thickness of the tape feeder.
Since the stripper 20 is formed as a separate part, the number of parts is increased, and the manufacture of the tape feeder is not easy. As shown in FIG. 1, the stripper 20 is separately manufactured of plastic and attached to the guide frame 11. The stripper 20 strips off the cover on the tape, and simultaneously prevents the parts from being removed from the tape. However, the stripper 20 is manufactured of plastic as a separate part, so that the durability is weak and manufacture and assembly of the part are not easy Also, assembly of the compression spring 21' is difficult. In other words, since one end of the compression spring 21' is installed on the guide frame 11 and the other end thereof is hung on the stripper 20, the compression spring 21' must be assembled simultaneously with the stripper 20, thereby resulting in difficult assembly.
Furthermore, it is difficult for the driving motor to perform indexing. The driving motor 16 is electrically controlled in response to the signal of the controller 63, but the inertia of an operating portion of the driving motor 16 cannot be controlled in this manner. Therefore, in practice, the accuracy of indexing is degraded with an increase in the number of indexing operations.